The principle of ink jet recording process is that a liquid or molten solid ink is jetted through a nozzle, slit or porous film to perform recording on a paper, cloth, film, etc. As methods for jetting the ink there have been proposed various methods such as electric charge controlling method in which an ink is jetted utilizing electrostatic attraction force, drop-on-demand method (pressure pulse method) in which an ink is jetted utilizing the oscillation pressure of a piezoelectric element, and heat ink jet method which comprises utilizing a pressure developed by the thermal formation and growth of air bubbles to jet the ink. These methods can provide an image having an extremely high precision.
As an ink for use in such an ink jet recording process there has been known and used an ink comprising various water-soluble dyes or water-dispersible pigments dissolved or dispersed in water or a liquid medium comprising a water-soluble organic solvent.
Studies have been made for improving the above described conventional ink. The ink for use in ink jet printer has been studied from the following standpoint of requirements:
(1) The ink provides an image having a high solid density as well as a high line density even on a plain paper such as copying paper and bond paper and causes no feathering; PA1 (2) The ink quickly dries up on a paper; PA1 (3) The ink causes no clogging and always exhibits excellent jetting stability and jetting response; PA1 (4) The ink exhibits a good storage stability over an long period of time; and PA1 (5) The ink does not undergo scorching with depositing (Kogation) on a heater used in the heat ink jet process. In order-to satisfy these requirements, many proposals have heretofore been made.
In particular, many proposals have heretofore been made for providing an image having a high density free of feathering on a plain paper. For example, JP-A-1-149872 proposes the use of a glycol selected from the group consisting of ethylene glycol and diethylene glycol in an amount of from about 5 to 10% by weight. Although this proposal satisfies the requirement for image quality on a plain paper, it leaves something to be desired in the prevention of clogging.
The present invention has been achieved to solve the above described problems in conventional techniques and to provide an ink satisfying all the requirements.